The invention concerns a surgical instrument for the removal of tissue, comprising an outer tube having an opening, for accepting tissue, in a distal region, preferentially in the vicinity of the distal end of the outer tube and with an inner tube disposed within the outer tube and having a rigid proximal region for transmitting forces or momenta acting on this proximal region to a distal region of the inner tube, preferentially to the distal end of the inner tube, and also with a cutting tool disposed at the distal region of the inner tube, preferentially on the distal end of the inner tube, for cutting tissue subjected to the influence of the cutting tool in the vicinity of the opening of the distal region of the outer tube, wherein the inner tube comprises a flexible region between its rigid proximal region and the cutting tool.
Instruments of the kind categorizing the invention are available in innumerable embodiments. Instruments, as used in the area of endoscopy and in particular in the area of arthroscopy typically have an outer tube having an opening in the distal region, frequently in the vicinity of the distal end of the outer tube, into which tissue can be accepted. An inner tube is disposed in the outer tube having a cutting tool disposed in a distal region, frequently at the distal end of the inner tube. The cutting tool can be directly formed onto the inner tube or can be a separately manufactured component which is connected to the inner tube e.g. by means of welding. The cutting tool can be used to separate out tissue at the location of use by rotating the inner tube relative to the outer tube. The removed tissue is then suctioned-off, together with rinsing liquid normally used in this type of operation, with the assistance of vacuum and passed through the inner tube.
With typical (linearly extending) instruments used in the art of endoscopy and in particular in the field of arthroscopy, it is however sometimes difficult or even impossible for the surgeon to move the cutting tool to the desired location (e.g. the lower side of the patella, the upper and lower regions of the femurcondyle or portions of the crescent-shaped menisci, in particular the front and back horns thereof) at which cutting of the tissue should be carried out. The term “tissue” herein refers to any kind of tissue, i.e. soft tissue, tissue of intermediate hardness (e.g. cartilage) or even very hard tissue (e.g. bone tissue). The term “cutting” accordingly refers to all conventional means of removal in this art, e.g. in particular cutting, milling etc.
In order to simplify advancement towards these locations which are not accessible or are at best accessible only with difficulty, other kinds of instruments are available which deviate from the typical linear shape, e.g. those in which the instrument is angled in the distal region. With the assistance of such instruments, it is easier to gain access to locations which are not accessible or are accessible only with great difficulty using the conventional linearly designed instruments.
It is immediately obvious that, when using such Instruments having a non-linear shape, the rigid proximal component of the inner tube must transfer the driving force or the driving momentum to the cutting tool disposed at the distal region, preferentially on the distal end. However, towards this end, one must pass through the non-linear transitional region between the proximal portion of the inner tube and the cutting tool. In other words, the Inner tube must transfer the driving force or the driving momentum past the non-linear transitional region to the cutting tool.
Towards this end, e.g. an instrument is described in EP-A-0,445,918 having a flexible transition region disposed between the rigid proximal region and the distal region. This flexible transitional region is configured in such a fashion that a plurality of discrete openings are provided at this location in such a fashion that the diameter of the inner tube is alternately reduced in the horizontal and vertical directions, each perpendicular to the longitudinal axis of the inner tube, so that only bridge regions are present in these locations, wherein neighboring bridges are however connected to each other.
The mutually connected bridges guarantee the flexibility of the inner tube in the transitional region while nevertheless facilitating a transfer of forces or momenta to the distally disposed cutting tool. However, the forces or momenta which can be transferred with a flexible transitional region of this kind are somewhat limited. The limitation of the forces or momenta which can be transferred to the cutting tool is also the intended purpose of this design, since the bridges also serve as intended breaking locations. Should the forces or momenta acting on the cutting tool exceed a predetermined limiting value, the bridges break. One thereby prevents the introduction of extremely large forces or momenta onto the cutting tool which could fracture same, wherein individual broken pieces of the cutting tool could gain entrance to the location of the operation and into the tissue.
As already mentioned, the forces or momenta which are to be transferred are limited. Precisely for the case of alternating loads which, for example, occur during oscillating operation of such instruments (continuous change of the rotation direction of the inner tube relative to the outer tube), the bridges can be quickly broken. On the other hand, oscillating operation is an optional mode of operation for an instrument of this type which is extremely useful, since precisely for tissue having intermediate hardness and for hard tissue it is often not possible to predict which rotational direction is suitable for removal of the tissue. This depends in part on the geometrical configuration of the tissue to be removed and on the direction from which one gains entrance to the tissue to be removed. In some of such cases, one can effect removal of the tissue using oscillating operation of the instrument, which would be difficult or even impossible using operation in only one single rotational direction. However, this necessitates transmission of the alternating load from the proximal region of the inner tube to the cutting tool.
It is therefore the purpose of the invention to propose an instrument having an inner tube with a flexible region, which can also be used with non-linear instruments, wherein the flexible region of the inner tube should have a sufficient degree of alternating load strength to be able to withstand the alternating loads during oscillating operation. Moreover, the inner tube should be easy to manufacture, since it is also a purpose of the invention to propose a tube per se, having a flexible region with sufficient strength with respect to alternating loads for withstanding same. Clearly, the inner tube itself must also be sufficiently leak-tight in precisely this flexible region such that the suctioned off tissue portions cannot escape out of the inner tube.